Fuselage pitot-static tube

ABSTRACT

Since, as a rule, there are several such PSTs on an aircraft, this results in a marked reduction in weight and aerodynamic drag, and savings in the required electric power in conjunction with a simultaneous increase in the accuracy of measurement of the angle of attack. All this permits a substantial increase in the competitiveness of the proposed fuselage Pitot-static tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/355,409 filed Sep. 24, 1999 (Attorney Docket No.85934.000004).

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable

REFERENCE TO A “SEQUENCE LISTING”

[0003] Not applicable

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] The invention relates to the determination of the flightparameters of flying vehicles or to other fields of science andtechnology which deal with flows of liquid or gas.

[0006] 2. Background Art

[0007] The measurement of flight parameters is one of the most importanttasks of the aeromechanics and aerodynamics of flying vehicles (FVs). Atthe present time, in order to measure the flight (flow) parameters useis made of Pitot-static tubes (PSTs) which are, frequently, mounteddirectly on the fuselage of the aircraft or on the body of any otherflying vehicle, and these PSTs actually measure parameters of the localflow, which is close to laminar. As a rule, several such PSTs aremounted on the flying vehicle and measure the local flow parameters. Thetrue flight parameters are determined on the basis of preliminarycalibrations.

BRIEF SUMMARY OF THE INVENTION

[0008] A Pitot-static tube mounted on the body or fuselage of an FV isknown from WO 94/02858. The known PST has a cylindrical tube mounted ona strut having curved leading and trailing edges which approach oneanother as the tube is neared from the base of the strut. The leadingorifice in the nose part of the tube for sensing the total pressure, andan orifice for sensing the static pressure at a certain distance fromthe nose of the tube. The tube has a heater for preventing the formationof ice. However, this Pitot-static tube cannot be applied fordetermining the angle of attack, since it lacks orifices for sensingpressure with the aid of which the angle of attack can be measured. Infact, as follows from the above-mentioned patent, this tube is notintended for these purposes. Moreover, the tapering of the strut, seenfrom the side, as the tube is approached leads, in conjunction withmaintaining the internal volumes required for installing airways andheaters, to a marked increase in the relative thickness of the profilesof the transverse cross-sections of the strut. This leads, in turn, inthe case of high sub-sonic speeds (Mach numbers of M=0.8-0.9) to theearlier appearance of local pressure shocks and a marked increase in theshock drag of such a Pitot-static tube.

[0009] A fuselage Pitot-static tube according to U.S. Pat. No. 4,615,213is known for determining the flight (flow) parameters—angle of attack,total pressure Po and static pressure Ps and, consequently, also theMach number M; it is an elongated axisymmetric body having a head partin the form of a hemisphere with groups of orifices on the axisymmetricbody for measuring pressures by means of which the flight (flow)parameters are determined with the aid of calibrations. At the sametime, the orifices for measuring the pressures by means of which thetotal pressure and angle of attack are determined are arranged on thehemispherical head part, while the orifices for measuring the staticpressure are arranged on the lateral (cylindrical) surface of theaxisymmetric body. For the purpose of mounting on the fuselage or bodyof the flying vehicle, this PST has a strut the profile of which has alens-shaped tranverse cross-section. The given PST has the followingdisadvantages:

[0010] a complicated design;

[0011] increased overall dimensions of the axisymmetric body;

[0012] increased aerodynamic drag in subsonic flight regimes;

[0013] increased required power for the heater of the anti-icing system;

[0014] increased design weight;

[0015] increased sensitivity of the total pressure, measured with theaid of the central orifice on the spherical head part, to variation inangle of attack, which leads to additional errors in measurement of thetotal pressure; such a dependence of the total pressure on the angle ofattack for a range of FVs is unacceptable.

[0016] The closest of the known technical solutions is disclosed in U.S.Pat. No. 4,378,696 for determining flight (flow) parameters—angle ofattack, total pressure Po and static pressure Ps, and thus the Machnumber M, which is an elongated axisymmetric body with a conical orogival head part where an orifice is arranged for sensing totalpressure, and which merges into a circular cylinder on whose surfaceorifices are arranged for sensing static pressure. Later, thiscylindrical surface merges into a conical one, on which orifices arearranged for sensing pressure for which the angle of attack is set upcorrespondingly, and then merges again into the cylindrical surface. Forthe purpose of being mounted on the fuselage or the body of an FV, thetube has a strut whose cross-section has a lens-shaped profile. Thegiven PST has the following disadvantages:

[0017] complicated design;

[0018] increased overall dimensions;

[0019] increased aerodynamic drag in subsonic flight regimes;

[0020] increased required power for the heater of the anti-icing system;

[0021] increased design weight;

[0022] low sensitivity of pressures, measured in orifices arranged on aconical part (and intended for determining α, to the angle of attack,which leads to increased errors in determining the angle of attack. Thisis caused by the following factors:

[0023] 1. As in the case described above, the given PST has an increasedmid-section of the axisymmetric body. Moreover, the increased dimensionof the mid-section is caused in the given instance by two circumstances.The first is that the cylindrical part of the axisymmetric body mergesinto a conical one on which orifices are arranged for sensing thepressure by which the angle of attack is determined. In order toincrease a little the sensitivity of the pressure sensed by means ofthese orifices of the angle of attack, the angle of taper must besufficiently large to lead to the necessity of increasing significantlythe diameter of the axisymmetric body behind the given conical part.

[0024] The second circumstance is bound up with the fact that althoughgroups of orifices for measuring pressure, which are used to determinetotal pressure, static pressure and angle of attack, are dispersed inthe given configuration, they are all situated on the same axisymmetricbody. There is a need to arrange inside the latter airways emerging fromall the indicated groups of orifices, a static pressure chamber and alsotubular electric heaters for the anti-icing system. The diameters of theairways and the TEHs cannot be less than a certain minimum values whichfor the airways are determined by the magnitude of the hydrodynamic lagand for the TEHs by the limiting values of the heat flux density and thetemperature of the surface of the heaters. The result is a high designsaturation, that is to say a complicated design of the axisymmetric bodyof the PST.

[0025] The circumstances indicated lead to an increase in the area ofthe mid-section, and consequently to an increase in the design weight,aerodynamic drag and power of the anti-icing system.

[0026] It should also be pointed out that transition from thecylindrical part to the conical one, and then again to the cylindricalone, can lead to separation of the flow behind the conical part and toan earlier appearance (in terms of the Mach number) of local pressureshocks. This, in turn, must lead to an increase in the aerodynamic drag.Moreover, the increased diameter of the axisymmetric body and thenon-optimum form of its tail part in conjunction with the strut alsolends [sic] an unfavorable aerodynamic interference (separation of theflow and earlier appearance of pressure shocks) in the area of the jointof the contracting tail part of the axisymmetric body of the PST behindthe line of maximum thickness of the lens-shaped aerodynamic profile ofthe strut. This also leads to a certain increase in the aerodynamic dragof such a PST.

[0027] It may also be noted that the presence of a conical part on theaxisymmetric body of a PST leads to the realization of additionalsupport on the cylindrical part lying in front, where the orifices formeasuring static pressure are arranged. As a result, the precisedetermination (without the introduction of corrections) of staticpressure requires that the orifices for sensing it must be sufficientlyfar from this conical part. The leads to the need to increase the lengthof the axisymmetric body, and also leads to a certain additionalincrease in the design weight, and requires additional power in theelectric heating anti-icing system.

[0028] 2. The lens-shaped profile of the strut is not optimum from thepoint of view of the aerodynamic drag in subsonic flight regimes. Thisleads to a substantial increase in the aerodynamic drag of the strut ofthe PST in subsonic flight regimes. Moreover, at very low Mach numbersthe increase in aerodynamic drag is caused by separation from the sharpleading edge of the strut with the lens-shaped profile, which alwaystakes place, since the leading edge is sharp, at local angles of attackother than zero. Since the lens-shaped profile is not optimum from thepoint of view of shock drag, at high subsonic speeds (M=0.8-0.9) theaerodynamic drag of such a PST is also increased very greatly. Althoughsweeping the leading and trailing edges of the PST strut postpones thesharp increase in shock drag, it leads to an increase given the samestagger of the axisymmetric PST body with respect to the fuselage, thatis to say given the same strut height, overall dimensions, weight andvolume of design and, consequently, also the required power of theanti-icing system.

[0029] 3. Electric heaters arranged inside the PST strut for preventingthe formation of ice on its leading edge, and thereby preventing theinfluence of this ice on measurement of pressure on the axisymmetricbody, are insufficiently efficient in use in the sense that they heatthe strut on which no orifices are arranged for measuring pressure. Thisleads to a substantial increase in weight and required electric power.

[0030] 4. The lens-shaped profile of the strut is not optimum from thepoint of view of:

[0031] a predisposition to the formation of ice;

[0032] the design of the anti-icing system.

[0033] This leads to a substantial increase in the required power of theanti-icing system of the actual strut of the PST, which is caused by thefollowing circumstances.

[0034] As is known (compare, for example, Bragg M. B., Gregorek G. M.,Lee J. D., Airfoil Aerodynamic in Icing Conditions. J. Aircraft, vol.23, No. 1., 1986), the formation of ice on a flying vehicle duringflight in the atmosphere takes place, first and foremost, in areasadjoining points where the flow is decelerated and in areas ofseparation of the flow from the leading edge (for example, the wing). Atthe same time, it is noted that sharp leading edges of the wing arefrequently more strongly subjected to the formation of ice thanrounded-off ones, since a stream with a separation of flow always formson them in the case of angles of attack other than zero. Such an area ofthe strut of a PST is an area adjoining its leading edge. Since thelens-shaped profile of the strut has a sharp leading edge, a stream withseparation of flow from the front edge can form even in the case ofsmall angles of attack, and this can lead to an intense formation ofice.

[0035] Since the TEHs of the anti-icing system are quite bulky andoccupy substantial volumes, they cannot be arranged inside the strut inthe immediate vicinity of the sharp edge of the lens-shaped profile ofthe strut. As a result, the TEHs on such a strut are arranged near theline of maximum thickness of the profile of the strut, while the heatingof the critical zone, where ice actually forms—the area near the leadingedge of the strut of the PST, results from heat transfer directly overthe structure of the strut, from the line of maximum thickness to theleading edge. Although struts of modem PSTs are made from materialswhich conduct heat very well and are very expensive (for example, fromnickel alloys), very large, inefficient heat losses reaching anestimated 50% are inherent in such a design.

[0036] Thus, the low coefficient of use for the energy supplied to theelectric heaters is characteristic of such a design of a PST. However,since they are quite bulky this leads to a significant increase in thedesign weight.

[0037] 5. The difference in the pressures measured at the conical partof the PST has a comparatively weak sensitivity to the change in theangle of attack, and this leads to increased errors in the measurementof the angle of attack. The increase in the aperture of the conesomewhat exceeds the sensitivity, but this leads to an increase in thediameter of the mid-section of the axisymmetric body of a PST, whichentails an increase in the design weight, the aerodynamic drag and therequired power of the anti-icing system. There are bodies where thissensitivity is substantially higher.

[0038] The nearest of the known symmetrical aerodynamic profilessuitable for use on the strut of a PST are the profiles of the NACA-OOXXseries (where XX is the relative thickness of the profile in percent);the disadvantage of these profiles resides in the rapid growth in shockdrag at high transonic numbers M. This is caused by the high degree ofthe differing effect of the profiles in the zone located behind themaximum thickness of the profile, which causes the earlier appearance ofthe pressure shock, as well as an increase in its intensity.

[0039] The objects of the invention are:

[0040] simplification of the design,

[0041] reduction in the overall dimensions,

[0042] reduction in the aerodynamic drag of the axisymmetric body of thePST,

[0043] reduction in the aerodynamic drag of the strut of the PST bydeveloping the contour of the symmetrical aerodynamic profile for thestrut of the PST which has a higher critical Mach number in theoperating range of numbers M=0-0.85 by comparison with known symmetricalaerodynamic profiles, in particular with a lens-shaped profile (composedof arcs of a circle) or profiles of a series NACA-OOXX for identicalvalues of the relative thickness,

[0044] reduction in the required power of the heating anti-icing system,

[0045] reduction in design weight,

[0046] an increase in the accuracy of determination of the angle ofattack on PSTs intended for subsonic non-manoeuvered flying vehicles.

[0047] The technical result is achieved by virtue of the fact that thefuselage Pitot-static tube comprising three groups of orifices fordetermining the total pressure, static pressure and angle of attack, andan axisymmetric body and strut for mounting an anti-icing system having,arranged between them, airways and electric heating elements, isconstructed in such a way that the orifices for determining the angle ofattack are arranged on the strut, whose cross-section is constructed inthe form of a subsonic aerodynamic profile with a rounded-off nose or atapered nose, and lie at some distance from the nose of the profile upto its maximum thickness.

[0048] For the purpose of a greater reduction in the aerodynamic drag ofthe fuselage sensor, the tail part of the axisymmetric body mayterminate with and may be smoothly joined to the aerodynamic profile ofthe strut in the region of its maximum relative thickness, while for thepurpose of reducing the aerodynamic drag at high subsonic speeds thetail part of the axisymmetric body can have a taper and base cut, andfor this purpose the trailing edge of the aerodynamic profile of thestrut can also have a base cut.

[0049] In order to compensate for the influence of the fuselage orsupport of the strut on the measured static pressure, the axisymmetricbody may have on the cylindrical part a swelling on which the orificesfor measuring the static pressure are arranged.

[0050] The aerodynamic profile of the strut can be constructedasymmetrically for the purpose of additionally increasing thesensitivity of the variation in pressure to the angle of attack and ofextending the range of the angle of attack.

[0051] For the purpose of an even greater reduction in the requiredpower of the anti-icing system, the electric heating elements of theanti-icing system may be displaced towards the leading edge of thestrut.

[0052] A simplification of the design of the axisymmetric body and asubstantial reduction in its diameter are achieved by virtue of the factthat the orifices for measuring pressure, which are used to measure theangle of attack, are arranged not on the axisymmetric body but on thestrut of a PST. Since the design weight is proportional to the cube ofits linear dimensions, given the same length of the axisymmetric body,reduction in its weight will be determined as the product of a certaincoefficient and the difference of the squares of the diameter of theaxisymmetric body of the PST prototype and the proposed PST. Since theaerodynamic drag of the axisymmetric body given a zero angle of attackof the PST is proportional to the area of its mid-section, the reductionin the aerodynamic drag of the PST were it to have the same form as thePST prototype would also be proportional to the difference of thesquares of the diameters of the axisymmetric body of the PST prototypeand the proposed PST. However, since the form of the axisymmetric bodyof the proposed PST does not have additional steps (conical step with asubsequent swelling) as in the PST prototype, there will be noseparation of flow on it nor any appearance of pressure shocks behindthe conical step. Thus, the reduction in the aerodynamic drag will beeven larger. Since the required power for heating the axisymmetric bodyis proportional to the area of the surface of revolution of theaxisymmetric body, reduction in the power for heating the proposed PSTby comparison with the PST prototype (given the same temperature oftheir surface) is proportional to the difference between the diametersof the axisymmetric body of the PST prototype and the proposed PST.Moreover, reduction in the required power of the heating system leads toa reduced weight of the TEHs.

[0053] The strut of the PST can be constructed in such a way that itscross-sections have the form of a subsonic aerodynamic profile with achord of length B, a rounded-off leading edge and a sharpened or bluntedtrailing edge interconnected by the smooth lines of the contour of theupper and lower surfaces. The lower part of the contour of the profileis symmetrical to the upper part relative to the profile chord. Theleading edge of the profile has a radius of curvature Rc which is in therange of Rc=0.030 * B-0.034 * B, in that the maximum relative thicknessof the profile C is in the range of C=0.146-0.156 and is arranged at adistance of X=0.3 * B-0.6 * B, measured from the leading edge along itschord. The radius of curvature of the upper part of the profile contourincreases smoothly along the profile chord with increasing distance Xfrom the rounded-off leading edge up to the values of X=(0.3-0.6)* B forwhich part of the contour has a virtually rectilinear form up to thevalues of R=5.5 * B-15. * B, it being the case that distance Yu,measured from the profile chord along the normal to it upwards to theupper part of the profile contour, increases smoothly to its maximumvalue of Yumax=0.074 * B=0.078 * B. The distance Yu further decreasessmoothly along the direction towards the trailing edge, the radius ofcurvature firstly decreases smoothly down to the values of R=0.6 *B-1. * B for X=0.82 * B-0.95 * B, and thereafter it increases smoothlyup to the values of X=0.92 * B-0.95 * B, where the convex part of thecontour is joined smoothly to its concave tail part and, further, theradius of curvature of the concave part of the contour decreasessmoothly, reaching at the trailing edge of the profile values ofR=0.05 * B-0.5 * B, the angle between the tangent to the profile contourand the chord of the profile at its trailing edge being 3-6 degrees forX=B. As the results of the calculations showed, the selected form of thecontour and the distribution of curvature along its chord permits asubstantial reduction in the shock drag of the profile both incomparison with the profile of the PST prototype (lens-shaped) and incomparison with the profile prototype (NACA 0015). Since when producingflying vehicles it is possible in a real design to realize theoreticalcoordinates of the profile contour only with a certain limited accuracydetermined by the aggregate deviations of the actual coordinates of thepoints of the profile contour from the theoretical ones, whichdeviations accumulate at all stages of design and manufacture, thecoordinates of the profile contour corresponding to the given inventionmust be in the interval of values given by Table 1: TABLE 1 X/B Yu/B−YI/B 0.0000 0.000 0.000 0.0333 0.0346-0.0376 0.0346-0.0376 0.06400.0477-0.0507 0.0477-0.0507 0.1044  0.570-0.0600 0.0570-0.0600 0.21710.0690-0.0730 0.0690-0.0730 0.3242 0.0725-0.0765 0.0725-0.0765 0.40130.0739-0.0779 0.0739-0.0779 0.5204 0.0736-0.0776 0.0736-0.0776 0.59920.0721-0.0761 0.0721-0.0761 0.7105 0.0681-0.0721 0.0681-0.0721 0.80670.0602-0.0642 0.0602-0.0642 0.8603 0.0510-0.0550 0.0510-0.0550 0.94640.0248-0.0288 0.0248-0.0288 1.0000 0.0000-0.0160  0.0000-0.01600

[0054] In practice, additional design and aerodynamic requirementsfrequently arise, which amount to comparatively small changes in therelative thickness of the profile and are expressed in the fact that thedimensionless ordinates, referred to its chord, of the contours of theupper Yu/B and lower YI/B surfaces differ from correspondingdimensionless ordinates of the base profile of the original relativethickness by equal constant numerical factors.

[0055] The transition to a different relative thickness for the profileby the given invention is possible by multiplying the ordinate of itscontour by equal constant numerical factors Ku for the upper and KI forthe lower parts of the contour, the radii of curvature of the leadingedge of the profile over its upper and lower surfaces varying in afashion proportional to the square of the coefficients, and thenumerical values of these factors having to be in the ranges of0.8<Ku<1.07 and 0.8<KI<1.07. Owing to the fact that the strut of the PSTis constructed in such a way that its cross-sections have the form of asubsonic aerodynamic profile with a rounded-off nose, and not of alens-shaped profile, as on the PST prototype, its aerodynamic drag can,as indicated by calculations, be reduced by 2-2.5 times in the case ofthe number M=0.8-0.9.

[0056] It is known that the formation of ice during flight in theatmosphere chiefly affects areas of flow deceleration or areas where aseparation of flow is formed. Owing to the occurrence on them of streamswith flow separation, sharp leading edges are frequently more subject tothe formation of ice than are rounded-off ones. Since, by contrast withthe lens-shaped profile, where even at small angles of attack a streamis formed with separation of flow from the leading edge, there is noseparation of flow at small angles on a subsonic aerodynamic profilewith a rounded-off nose, the strut of the proposed PST is less subjectto the formation of ice than the strut of the PST prototype. Moreover,in the case of the strut of the PST prototype, because of the fact thatit has a cross-section in the form of a lens-shaped profile, it isdifficult or virtually impossible to arrange the electric heaters of theanti-icing system immediately next to the nose of the profile, since thevolumes required for this are not present inside. Consequently, theelectric heaters for such a PST are arranged not in the nose itself(which is most subject to the formation of ice) but near the centre ofthe profile. As a result, heating of the nose is due to heat transferalong the strut, and this causes large power losses (estimated at up to50%). In the proposed PST, the radius of the nose of the subsonicaerodynamic profile can be made sufficiently large to permit theelectric heaters to be arranged directly in the nose of the strut, andthereby to reduce power losses by 25-30%.

[0057] Since the critical Mach number (at which pressure shocks occur)on the subsonic aerodynamic profile with a rounded-off nose, inparticular on the profile according to the given invention, can besubstantially lower than on a lens-shaped one, the sweep angle of thestrut of the PST designed for flights with M=0.8-0.9 can be madesubstantially smaller for the proposed PST than for the strut of the PSTprototype. As estimates indicate, for the same height of the struts andprofile chord this yields a reduction in the length of the PST and again in design weight by 10-15%.

[0058] Since the sensitivity to variation in the angle of attack ofpressures measured on a subsonic aerodynamic profile with a rounded-offnose is substantially higher than on a cone, the error in measurement ofthe angle of attack is substantially lower for the proposed PST than forthe PST prototype.

[0059] The trailing edge of the aerodynamic profile of the section ofthe strut can be constructed with a base cut for the purpose ofadditionally reducing the shock drag at numbers of M=0.8-0.9 involving,in terms of Mach number, occurrences of pressure shocks and theirdisplacement to the tail of the profile owing to the lesser diffusoreffect of the profile behind the point of its maximum thickness.Constructing the tail part of the axisymmetric body with a taper andbase cut also permits, in a fashion analogous to the aerodynamicprofile, a reduction in the shock drag of the PST. If the tail part ofthe axisymmetric body starts to taper in the area of the maximumthickness of the profile of the strut, a strong diffuser which leads toan earlier occurrence of local pressure shocks and an increase inaerodynamic drag is formed in the area of the joint of the tail part ofthe body and the strut. In the case when the axisymmetric body isconstructed in such a way that its tail part terminates with and issmoothly joined to the aerodynamic profile of a strut in the area of itsmaximum relative thickness, there is an improvement in the interferenceof the axisymmetric body and strut, and there is an additionalsubstantial decrease in the aerodynamic drag of the PST because of theabsence of an additional diffuser. Owing to the fact that theaerodynamic profile of the strut can be constructed asymmetrically,there is an increase in the sensitivity of pressure to the angle ofattack, and it is thereby possible additionally to increase the accuracyof measurement of the angle of attack; moreover, the range of the angleof attack can be widened owing to the asymmetry of the profile. Tocompensate the effect of deceleration from the strut on the measurementof static pressure, the axisymmetric body can have on the cylindricalpart a swelling on which orifices for measuring static pressure arearranged. Owing to the acceleration of the flow on this swelling, it ispossible to find an area where the deceleration from the strut iscompensated for by this acceleration and, consequently, the precisestatic pressure can be selected from the indicated orifices. Because ofthe displacement of the electric heating elements towards the leadingedge of the strut, there is a substantial reduction in the inefficientthermal losses by comparison with the PST prototype, and a reduction inthe required power for heating.

[0060] The construction of the invention, however, together withadditional objects and advantages thereof will be best understood fromthe following description of specific embodiments when read inconnection with accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0061]FIG. 1 shows a side-elevational view of one of the variants of theproposed PST;

[0062]FIG. 2 is a cross-sectional view taken along the line A-A of FIG.1;

[0063]FIG. 3 is a top-plan view on the PST according to FIG. 1;

[0064]FIG. 4 shows an example of a PST with a strut comprising anaerodynamic profile intended for use at numbers M=0.8-0.9 with a basecut;

[0065]FIG. 5 is a cross-sectional view taken along the line A-A of FIG.4;

[0066]FIGS. 6 & 7 show variants of the proposed PST with an axisymmetricbody having a taper and base cut in the tail part;

[0067]FIG. 8 shows a side-elevational view of an alternative embodimentof the invention with an axisymmetric body whose tail part terminateswith and is smoothly joint to the aerodynamic profile of the strut inthe area of its maximum relative thickness;

[0068]FIG. 9 is a cross-sectional view taken along the line A-A in FIG.8;

[0069]FIG. 10 is a cross-sectional view taken along the line B-B in FIG.8;

[0070]FIG. 11 is a cross-sectional view taken along the line C-C of FIG.8;

[0071]FIG. 12 shows a side-elevational view of a variant of the proposedPST with an asymmetric aerodynamic profile of the strut;

[0072]FIG. 13 is a cross-sectional view taken along the line A-A of FIG.12;

[0073]FIG. 14 is a top plan view of the PST according to FIG. 12;

[0074]FIG. 15 shows a side-elevational view of further variant of a PSTaccording to the invention on which an axisymmetric body on thecylindrical part has a swelling on which there are arranged orifices formeasuring static pressure;

[0075]FIG. 16 shows a top plan view of the PST according to FIG. 15;

[0076]FIG. 17 shows a side-elevational view of a variant of the PSTaccording to invention with electric heating elements of an anti-icingsystem which are displaced towards the leading edge of the strut;

[0077]FIG. 18 shows a cross-sectional view taken along the line A-A ofFIG. 17;

[0078]FIG. 19 shows a diagram with the variation in the ratio of thetotal pressure P2, sensed by the orifice 2, to the true total pressurePo for the proposed PST and a PST with a spherical head part, as afunction of the angle of attack for a Mach number M=0.8;

[0079] FIGS. 20-23 are diagrams showing examples of the dependence ofthe drag coefficients Cd of lens-shaped and subsonic aerodynamic profilewithout a base cut and with a base cut for different values of the angleof attack, Mach numbers M and maximum relative thickness of the profileC/B, where C is the maximum thickness and B the profile chord;

[0080]FIG. 24 is a side elevational view of a PST showing how the sweepof the strut at the leading edge affects the magnitude of the chord ofthe cross-section of the strut when the internal volumes of the sectionare maintained. The following designations are introduced here: ABCD isthe lateral projection of the strut with a sweep of χ1 and a chord ofsection b1, S1 is its area; AB1C1D1 is the lateral projection of thestrut with a sweep of χ2>χ1 and a chord b2=b 1, its area isSAB1C1D1>SABCD; ABC1D2 is the lateral projection of the strut with asweep of χ2, the area of which is SABC1D2=SABCD, but its chord is b3<b1;V is the rate of flow, and V⊥, V∥ are the velocity components normal tothe leading edge and, correspondingly, parallel to it;

[0081]FIG. 25 is a diagram showing the dependence of the angularcalibration coefficient æ_(α),=(P6-P7)/(P2-P3) for determining the angleof attack for the proposed PST, and also for the PST prototype, in whichthe orifices for determining the angle of attack are arranged on theconical part of the axisymmetric body, where Pi are the pressuresmeasured at the corresponding i orifices; 2, 3 denote orifices arrangedcorrespondingly in the nose part and on the cylindrical surface of theaxisymmetric body, both on the proposed PST and on the PST prototype;the numerals 6, 7 denote orifices on the strut in the proposed PST or onthe conical part of the axisymmetric body in the case of the PSTprototype.

[0082]FIG. 26 is a diagram showing a comparison of the dependencies forthe symmetric and asymmetric aerodynamic profiles of the strut;

[0083]FIGS. 27 & 28 are diagrams showing the basic elements of theprofile for the given invention, and a comparison of the contrary of thegiven profile an the NACA-0015 profile;

[0084]FIG. 29 shows the distribution along the profile chord of thecurvature K(A quantity inversed to the radius of curvature) for thechord the profile designed in accordance with the given invention;

[0085]FIG. 30 is a diagram showing the comparison of the calculatedmagnitudes of the shock-drag coefficient Cdw of the given profile andthe profile prototype;

[0086]FIGS. 31a-31 g show the schematical cross-sectional views ofvariants of the strut.

DETAILED DESCRIPTION OF THE INVENTION

[0087] The fuselage Pitot-static tube (FIG. 1) comprises an axisymmetricbody 1 in whose nose part an orifice 2 is arranged for determining totalpressure; orifices 3 for sensing static pressure are arranged on thelateral surface. TEHs 4 of an anti-icing system are located inside theaxisymmetric body 1. The axisymmetric body is mounted on the strut 5,which has the form of a subsonic aerodynamic profile with a rounded-offnose on which there are arranged at a distance from the nose up to itsmaximum thickness orifices 6, 7 for determining the angle of attack,while TEHs 8 are arranged inside the strut. To reserve the orifices,several orifices 6, 7 can be arranged in each case on the upper andlower surfaces of the profile. The PST is mounted on the fuselage withthe aid of a flange 9. Pressures from the orifices 2, 3, 6, 7 are leadout of the PST with the aid of airways 10 and nozzles 11, while heatingthe axisymmetric body and strut of the PST is performed with the aid ofelectric heaters 4, 8 via an electric connector 12.

[0088] The fuselage Pitot-static tube operates in the following way.Pressures sensed by the orifices 2, 3, 6, 7 are transmitted via nozzles11 into a block of transducers which transforms the pressures intoelectric signals. These electric signals are sent into aninformation-processing block in which the flow (flight) parameters Po,Ps, α are determined in accordance with calibration dependencies.Electric energy is supplied to the TEHs 4 and 8 via the electricconnector 12 in order to prevent the formation of ice, which canstrongly distort the measurements or lead to obstruction of the orificesand failure of the PST. The electric TEHs 4 and 8 heat the externalenvelope of the axisymmetric body 1 and of the strut 5, and also theairways 10, which are manufactured, as a rule, from highly thermallyconductive materials (for example, nickel). The power of the TEHs and ofthe electric energy supplied is selected so as to prevent the formationof ice on surfaces of the axisymmetric body 1 and strut 5 and in theorifices 2, 3, 6, 7.

[0089] The aerodynamic profile of the strut 5 has a base cut 13 in orderfurther to reduce the aerodynamic drag at numbers of M=0.8-0.9 (FIG. 5).

[0090] The tail part of the axisymmetric body 1, is constructed with ataper and a base cut 14 in order further to reduce the aerodynamic drag(FIGS. 6, 7).

[0091] The tail part of the axisymmetric body is joined smoothly withand terminates in the area of the maximum relative thickness of theaerodynamic profile C (FIGS. 8-11) for the purpose of additionallyreducing the aerodynamic drag by improving the interference between theaxisymmetric body 1 and strut 5.

[0092] An asymmetric aerodynamic profile of the strut may be applied forthe purpose of additionally increasing the sensitivity to variation inthe angle of attack and thereby increasing the accuracy of itsdetermination, and also for the purpose of extending the range ofmeasurement of the angle of attack (FIGS. 12-14).

[0093] In order to compensate for the effect of deceleration from thestrut on the measured static pressure, the axisymmetric body 1 can haveon the cylindrical part a swelling 15 (FIGS. 15, 17) on which there arearranged orifices 3 for measuring the static pressure.

[0094] For the purpose of further reducing the required power of theanti-icing system, the electric heaters 8 can be displaced towards theleading edge of the strut 5 (FIGS. 17, 18).

[0095] It is expedient to make use on the strut of the PST of profileswhich are normal to its axis of sections of maximum thickness, which isarranged at a distance of X=0.3 * B-0.6 * B from the leading edge, whichprofiles have leading and middle parts which are as swollen as possibleand a maximum critical Mach number for a given range of permissiblerelative thicknesses of the profile and an adequate range of workingangles of attack within the limits of up to α=18-20%. An aerodynamicprofile in accordance with the given invention meets these requirements.

[0096]FIGS. 27 & 28 show the aerodynamic profile in accordance with thegiven invention, having a rounded-off leading edge 16 and a sharpened orblunted trailing edge 17 which are interconnected by the smooth lines ofthe contours of the upper 18 and lower 19 surfaces; its leading edge 16is constructed with a radius of curvature of the upper and lowersurfaces of the profile, referred to its chord Rc/B, which is in therange of 0.03-0.034. The maximum relative thickness of the profile isapproximately equal to 0.15 and arranged at a distance of 0.3 * B-0.6 *B from its leading edge, while the ordinates of the contours, referredto the profile chord and laid off along the normal thereto, of the upperYu/B and lower YI/B surfaces at a distance, referred to the profilechord, from its leading edge of X/B are arranged in the ranges set forthin Table 1. The ranges, presented in Table 1, of the ordinates of theupper and lower surfaces of the profile correspond approximately topermissible design/technical deviations of its actual coordinates fromtheir theoretical values. The smoothness of the profile according to thegiven invention ensures a continuous and smooth variation in thecurvature of its contour. The distribution of the curvature of thecontour (magnitude, inverse radius of curvature) along the profile chordis present in FIG. 14 for the upper part of the contour (curve 20) andfor the lower part of the contour (curve 21).

[0097] The design merit of the given profile as applied to the strut ofthe PST according to the given invention is to ensure adequate fullnessof its nose and middle parts, which substantially facilitates thearrangement of the airways and heating elements of the PST in theprofile contour.

[0098]FIGS. 29 and 30 also show calculated estimates of the magnitudesof shock drag for the proposed profile 22 and profile of the prototype23, which illustrate the marked advantage of the proposed profile.

[0099] The basic aerodynamic advantage of the given profile bycomparison with known profile analogues of close relative thickness inthe case of its use on the strut of a PST according to the giveninvention is the increased value of the critical Mach number, whichrenders it possible to operate on its subcritical values in theoperating range of flight speeds which is characteristic of subsoniccivil aircraft, in conjunction with a moderate angle of sweep of thestrut of the PST. The high aerodynamic efficiency of the profileaccording to the given invention is caused by the smoothness of itscontour and the rational combination of the basic geometrical parameters(indicated magnitudes of the distances of the points of the profilecontour from its chord, its radii of curvature and the angles of slopeof the tangents to the contour). The form of the profile contouraccording to the given invention is determined so as to achieve in theleading part of the profile a level of the magnitudes of the rarefactionof the flow which is lower given identical values of the angle of attack(by comparison with the prototype NACA OOXX) in the case of maximumprofile lift in the range of numbers M=0.2-0.5 and, correspondingly, alarger range of non-separated profile flow; in this case, a pressuredistribution close to a “shelved” distribution is realized in thetransonic range and has a less intense (by comparison with theprototype) pressure shock, and thereby a value of the shock drag whichis 1.5-3 times lower.

[0100] The following may be achieved by using the invention on subsonicnon-manoeuvrable aircraft:

[0101] design simplifications,

[0102] reductions in overall dimensions,

[0103] reductions in aerodynamic drag,

[0104] reductions in the required power of the anti-icing system of aPST,

[0105] weight reductions,

[0106] increase in the accuracy of measurement of the angle of attack.

[0107] Let us demonstrate this.

[0108] 1. Design simplification is achieved owing to the fact that theorifices for tapping pressure and on the basis of which the angle ofattack is determined are arranged not on the axisymmetric body of a PST,where the orifices for tapping total and static pressures are stillarranged, but on the strut of a PST (FIGS. 1-3). The design saturationof a PST is very high, because there are airways departing from each ofthe indicated groups of orifices, and it is also necessary to arrangeelectric heating elements of the anti-icing system inside theaxiymmetric body and strut. As a result of the transfer of the orificesfor measuring angle of attack from the axisymmetric body to the strut,the design saturation is decreased, and the construction of theaxisymmetric body and the entire proposed PST with the strut issubstantially simplified.

[0109] 2. As a result of the transfer of the orifices for tappingpressure, by means of which the angle of attack is determined, from theaxisymmetric body onto the strut, the diameter d of the axisymmetricbody is substantially decreased (FIGS. 1-3). The design studies carriedout indicate that the diameter of the axisymmetric body of the proposedPST can be reduced by approximately 25% by comparison with the PSTprototype (in conjunction with the same diameters of the internalairways and electric heating elements; only because of the absence ofthe conical part on the axisymmetric body).

[0110] Moreover, as a result of the absence on the axisymmetric body ofthe proposed PST of a conical part, an additional support is lacking onit which is realized on the PST prototype in the area of arrangement ofthe orifices for measuring static pressure. As a result, given the sameaccuracy of measurement of the static pressure (without the introductionof corrections), the length (FIGS. 1-3) of the axisymmetric body up tothe strut can be realized on the proposed PST to be shorter than on thePST prototype. Estimates show that this reduction in length is about20%.

[0111] One more factor promoting the reduction of the overall dimensions(length of a PST) is the application on the strut of a subsonicaerodynamic profile with a rounded-off nose, as a result of which thesweep of the leading edge of the strut (FIG. 24) can be substantiallyreduced (see item 3 for more detail). As a result, given the same heightof the strut and tuning of the PST to the same Mach numbers, the lengthof the strut can be reduced by 5-7%, it being possible for the overalllength of the PST (axisymmetric body with strut) to be reduced by25-27%.

[0112] 3. The aerodynamic drag of the axisymmetric body can berepresented by the formula D=Cd.q-S, where Cd is the drag coefficient, qis the dynamic pressure and S is the characteristic area. Thecharacteristic measure of the axisymmetric body of the PST may be takenas the area of its mid-section S=π{fraction (2/4)}, where d is thediameter of the mid-section. Thus, if the axisymmetric body of theproposed PST were to be geometrically similar to the axisymmetric bodyof the PST prototype (that is to say given the preservation of the samemagnitude of Cd), the drag of the axisymmetric body of the proposed PSTwould be reduced by about 45% given the same dynamic pressures (that isto say given the same magnitude of the speed V and Mach number M) as aresult of the reduction in the diameter d by 25% (see item 2 above).However, since the form of the axisymmetric body of the proposed PSTdoes not have additional steps (conical part with subsequent swelling ofthe diameter, as in the case of the PST prototype), it will not exhibitany separation of flow nor the occurrence of pressure shocks after theconical part. Thus, as estimates show, the magnitude of the dragcoefficient for the axisymmetric body of a proposed PST can be reducedby approximately 7-10%. As a result, the drag of the axisymmetric body Xof the proposed PST is about 50% of the PST prototype.

[0113] Owing to the fact that the strut of the proposed PST isconstructed in such a way that its cross-sections normal to the leadingedge (FIGS. 1-3) have the form of a subsonic aerodynamic profile withthe rounded-off nose, in particular an aerodynamic profile according tothe given invention, and not of a lens-shaped profile, as in the PSTprototype, the aerodynamic drag of such a profile for numbers ofM=0.8-0.9 can, as indicated by calculations (FIG. 20), be reduced by2-2.5 times: The strut can be constructed with a sweep at the leadingand trailing edges in order to postpone, in terms of Mach numbers, theon-set of a crisis (occurrence of pressure shocks) and thereby areduction in shock drag. However, as a consequence of the fact that thecritical Mach number M at which pressure shocks occur is substantiallylarger for a profile with a specialized subsonic aerodynamic profilewith a rounded-off nose than for a lens-shaped profile, the sweep of thestrut with the subsonic aerodynamic profile can be made substantiallysmaller than for the strut with the lens-shaped profile. Calculationsindicate that for the number M=0.9 it is possible to reduce the sweep ofthe strut at the leading edge by 7-10° on the proposed PST by comparisonwith the PST prototype. When a compressed stream of gas flows around thestrut, the component of the velocity V⊥ perpendicular to the trailingedge influences the shock drag (FIG. 24). Consequently, given thepreservation of the same internal volumes of the sections of the strutwhich are required for the lines of the airways and the electric heatinganti-icing system, and the same relative thickness of the profile C,which chiefly strongly affects the onset of crisis (FIG. 21), (sharpincrease in the shock drag), the area of the lateral surface of thestrut can be reduced, which yields a substantial gain in terms of itsweight. Calculations and design studies indicate that this reduction inthe weight of the strut is roughly 20% for the proposed PST bycomparison with the PST prototype. Given an angle of attack, theproposed PST with a strut whose cross-sections have the form of asubsonic aerodynamic profile with a rounded-off nose also has asubstantial gain in terms of drag by comparison with the PST prototypehaving sections of the strut in the form of a lens-shaped profile.Since, given an angle of attack, a flow is realized on the lens-shapedprofile with separation of flow from the sharp leading edge, the dragcoefficient of such a profile is substantially higher than for thesubsonic aerodynamic profile with a rounded-off nose, where anon-separated flow is realized up to comparatively large angles ofattack (α=18°) and Cd is substantially lower (see FIG. 22, where Cd(a)of such profiles is given, by way of example, for the number M=0.1). Thereduction in drag indicated takes place here in the case both of verylow and of high Mach numbers.

[0114] The subsonic aerodynamic profile of the strut on the proposed PSTis constructed with a base cut to achieve an even greater postponement,in terms of Mach number, of the sharp rise in shock drag (FIGS. 4, 5).As a result of the presence of the base cut on the profile, a smallerdiffusor is realized in the area between the maximum relative thicknessand the tail part of the profile. In conjunction with an insignificantrise in the base drag, this permits a substantial increase in thecritical Mach number for the profile and a postponement of the sharpincrease in shock drag at high Mach numbers, and thereby a decrease inthe shock drag for large numbers M. The dependencies Cd(M) are presentedby way of example in FIG. 9d for the aerodynamic profile without andwith a base cut. It is to be seen that, despite a certain slightincrease in the base pressure (see, for example, Cd for M=0), in thecase of a calculating number M=0.9 the aerodynamic profile with the basecut has a substantially lower drag coefficient than the aerodynamicprofile without the base cut. In a fashion analogous to what has beenset out above, the strut of the proposed PST can, as a result of the useon it of an aerodynamic profile with a base cut, have a sweep at thetrailing edge which is less by 3-5° than the strut of the PST prototypewith a lens-shaped profile which, as indicated by the calculations andthe design studies carried out, in turn yields a reduction of about 10%in the design weight.

[0115] As indicated by the calculations carried out, an additionalreduction in the aerodynamic drag coefficient at numbers of M=0.8-0.9can be obtained by constructing the tail part of the axisymmetric bodywith a taper and base cut (FIGS. 6, 7). A positive effect—a reduction inthe drag coefficient of the axisymmetric body by 10-15%—is also achievedin this case, as for the case described above of the aerodynamic profilewith a base cut, owing to the reduction in diffusor effect in the tailpart of the axisymmetric body.

[0116] An additional reduction in the aerodynamic drag on the proposedPST can be ensured by virtue of the fact that the tail part of theaxisymmetric body terminates with and is smoothly joined to theaerodynamic profile of the strut in the area of its maximum relativethickness (FIGS. 8-1 1). A positive effect is achieved in this caseowing to the organization of the underlying interference of the tailpart of the axisymmetric body of the PST and strut. Since, in this case,there is no additional diffusor in the area of the joint of the taperingtail part of the axisymmetric body and the tail part of the profile ofthe strut, success is therefore achieved in avoiding the occurrence ofseparation of the flow and local pressure shocks. As indicated byestimates, the result is that the drag of the entire PST can beadditionally reduced by 10-15%.

[0117] 4. The required power of the heating anti-icing system of theaxisymmetric body of the proposed PST can also be substantially reducedby comparison with the axisymmetric body of the PST prototype. Given thesame heat emission of the axisymmetric body and the same temperature ofthe surface, the required power is proportional to the area of itslateral surface, πdl, that is to say depends linearly on the diameter dof the PST and the length 1. Since in accordance with item 2, thediameter d of the axisymmetric body of the proposed PST can be reducedby 25%, and its length by 20%, the overall reduction in the requiredpower of the anti-icing system is about 40% by comparison with theaxisymmetric body of the PST prototype. Together with the reduction inthe required power of the anti-icing system of the axisymmetric body ofthe proposed PST, there is also a substantial reduction in the requiredpower for heating the strut. This is associated with two circumstances.The first is that non-separated flow around the rounded-off nose of thesubsonic aerodynamic profile of the strut of the PST is realized on theproposed PST, as a result of which the leading part of the strut of theproposed PST is less subject to icing than the strut of the PSTprototype with a lens-shaped profile. Estimates indicate that for thisreason the required power for heating the strut can be reduced by15-20%. The second circumstance is linked to the fact that on the strutof the proposed PST with a subsonic aerodynamic profile with arounded-off nose the internal volumes permit the electric heatingelements to be arranged directly in the nose of the aerodynamic profile,which is most subject to icing (FIGS. 17, 18). There is a substantialcurtailment of inefficient thermal losses as a result. The calculationsand design studies carried out indicate that for this reason the powerrequired for heating the strut can be reduced further by about 20-25%.Moreover, owing to the reduction, indicated in item 3, in the sweep atthe leading edge of the strut of the proposed PST, there is a certainreduction in the extent of the leading strut from its base up to theaxisymmetric body, and therefore in the required area of heating. Theoutcome is a further reduction of approximately 5% in the required powerof the anti-icing system. To sum up, the required power of theanti-icing system of the proposed PST is reduced by 40-45% by comparisonwith the PST prototype.

[0118] 5. A reduction in weight of the proposed PST is achieved owing tothe decreases, indicated in items 2 and 3, in the dimensions of themid-section of the axisymmetric body and in the area of the lateralsurface of the strut as a consequence of lending the latter a lessersweep. Moreover, decreasing the required power of the electric heatingelements (see item 4) also leads to a decrease in the extent of theelectric heating elements and in their mass. As shown by thecalculations and design studies carried out, the design weight of theproposed PST can be reduced by 25-30% by comparison with the prototypeowing to the circumstances indicated.

[0119] 6. The increase in accuracy of the measurement of the angle ofattack on the proposed PST by comparison with the PST prototype isachieved as a result of the fact that the orifices for tappingpressures, by means of which the angle of attack is determined, arearranged on the strut, which has cross-sections in the form of asubsonic aerodynamic profile, at a distance from the nose of the profileup to its maximum thickness, and not on the conical part of theaxisymmetric body. It is clear from the dependencies, presented in FIG.11, of the angular coefficient æ_(α)(α), obtained on the basis ofexperimental data, that the derivative$\frac{\partial æ_{\alpha}}{\partial a}$

[0120] for the orifices on the aerodynamic profile in the range ofangles of attack of a=0-20% is substantially (8 times) higher than forthe orifices arranged on the conical surface of the axisymmetric body ofthe PST prototype. The error in the determination of the angle of attackcan be written in the form${\delta\alpha} = {{\frac{\partial a}{\partial æ_{a}}.\delta}\quad {p/q}}$

[0121] .δp/q where q is the dynamic pressure and δp is the error in themeasurement of the pressure drop P7-P6. Thus, given an error in the realpressure transducers of p=0.15 mm mercury column for M=0.2, the error inmeasurement of the angle of attack on the proposed PST has a magnitudeof 0.05° in the indicated range of the angles of attack, while thefigure for the PST prototype is 0.4°. Thus, the accuracy ofdetermination of the angle of attack for the proposed PST is increasedby 8 times. An additional increase in the accuracy of measurement of theangle of attack can be achieved by applying an asymmetric aerodynamicprofile of the strut (FIG. 26).

[0122]FIGS. 31a to 31 g are showing schematic cross-sectional views ofvariants of the strut of the PST. As can be seen FIGS. 31a-31 c arepolygonal strut profiles with a tapered nose, which advantageously maybe applied for supersonic airflow. FIG. 31d shows a strut with a taperednose but curved contours.

[0123]FIGS. 31e to 31 g are showing cross sections of the strut withrounded-off nose. FIG. 31f shows the NACA 0015 profile. FIG. 31g is theoptimized strut cross section according to FIG. 5.

[0124] Thus, the results presented here of computational andexperimental research and design studies clearly show advantages interms of all the parameters indicated above and of the properties of theproposed PST by comparison with the PST prototype.

1. Fuselage pitot-static tube having a body and a strut, and comprisingorifices for determining total pressure, static pressure and angle ofattack, and wherein the orifices for determining the angle of attack arearranged on the strut.
 2. The fuselage pitot-static tube of claim 1 inwhich the strut having a cross-section constructed in the form of asubsonic aerodynamic profile with a rounded-off or tapered nose.
 3. Thefuselage pitot-static tube of claim 1 in which an anti-icing systemhaving airways and electric heating elements is arranged inside thestrut such that the electric heating elements are displaced towards aleading edge of the strut.
 4. The fuselage pitot-static tube of claim 1in which the orifices for determining total pressure and static pressureare arranged on the body
 5. The fuselage pitot-static tube of claim 1 inwhich the body is axisymmetric.
 6. The fuselage pitot-static tube ofclaim 1 in which the orifices for determining total pressure and staticpressure are arranged on the axisymmetric body.
 7. Fuselage Pitot-statictube according to claim 1, in which the strut has a trailing edge with abase cut.
 8. Fuselage Pitot-static tube according to claim 5, in whichthe axisymmetric body has a tail part with a taper and a base cut. 9.Fuselage Pitot-static tube according to claim 5, in which a tail part ofthe axisymmetric body terminates with and is smoothly joined to a regionof maximum relative thickness of the aerodynamic profile of the strut.10. Fuselage Pitot-static tube according to claim 1, in which theaerodynamic profile of the strut is asymmetric.
 11. FuselagePitot-static tube according to claim 5, in which the axisymmetric bodycomprises a cylindrical part having a swelling on which the orifices formeasuring the static pressure are arranged.
 12. Fuselage Pitot-statictube according to claim 1, in which the aerodynamic profile of the struthas a chord of length B, a rounded-off leading edge, a sharpened orblunted trailing edge, which are arranged at the ends of the profilechord and interconnected by the smooth lines of the upper and lowerparts of a profile contour, wherein the leading edge of the profile hasa radius of curvature of the points of the upper and lower parts of thecontour Rc which is in the range of Rc=0.03*B-0.034*B, wherein themaximum relative thickness of the profile C is in the range ofC=0.146-0.156 and is arranged at a distance of X=0.3*B-0.6*B, measuredfrom the leading edge of the profile along its chord, and wherein theordinates, referred to the length of the profile chord, of the points ofthe upper part of the contour Yu/B and of the lower part of the contourYI/B, which are arranged at relative distances X/B, measured from theleading edge of the profile along its chord, are in the ranges set forthbelow: X/B Yu/B −Yl/B 0.0000 0.0000 0.0000 0.0333 0.0346-0.03760.0346-0.0376 0.0640 0.0477-0.0507 0.0477-0.0507 0.1044 0.0570-0.06000.0570-0.0600 0.2171 0.0690-0.0730 0.0690-0.0730 0.3242 0.0725-0.07650.0725-0.0765 0.4013 0.0739-0.0779 0.0739-0.0779 0.5204 0.0736-0.07760.0736-0.0776 0.5992 0.0721-0.0761 0.0721-0.0761 0.7105 0.0681-0.07210.0681-0.0721 0.8067 0.0602-0.0642 0.0602-0.0642 0.8603 0.0510-0.05500.0510-0.0550 0.9464 0.0248-0.0288 0.0248-0.0288 1.0000 0.0000-0.01600.0000-0.0160


13. Fuselage Pitot-static tube according to claim 12, of which theprofile contour has a smoothly changing curvature, wherein the radius ofcurvature of the upper and lower parts of the profile contour increasessmoothly along the profile chord with increasing distance X from therounded-off leading edge up to the values of X=0.3*B-0.6*B for whichpart of the contour has a virtually rectilinear form up to the values ofR=5.5*B-15.*B, it being the case that distance Yu, measured from theprofile chord along the normal thereto upwards to the upper part of theprofile contour, increases smoothly to its maximum value ofYumax=0.074*B=0.078*B, the distance Yu further decreases smoothly alongthe direction towards the trailing edge, the radius of curvature firstlydecreases smoothly down to the values of R=0.6*B-1.*B forX=0.82*B-0.9*B, and thereafter it increases smoothly up to the values ofX=0.92*B-0.95*B, where the convex part of the contour is joined smoothlyto its concave part and, further, the radius of curvature of the concavepart of the contour decreases smoothly, reaching at the trailing edge ofthe profile values of R=0.05*B-0.5*B, the angle between the tangent tothe profile contour and the profile chord at its trailing edge being 3-6degrees for X=B and the lower part of the contour being symmetrical tothe upper part relative to the profile chord.
 14. Fuselage Pitot-statictube according to claim 12, wherein the dimensionless coordinates,referred to its chord, of the contours of its upper Yu/B and lower Yl/Bsurfaces differ from the corresponding dimensionless coordinates of theprofile by constant equal numerical factors Ku for the upper surface andKl for the lower surface, and the dimensionless radii of curvature,referred to the profile chord, of the leading edge of this profile forits upper Ru/B and lower Rl/B surfaces differ from the correspondingdimensionless radii of curvature of the leasing edge for the upper andlower surfaces of the profile by the squares of just three constantnumerical factors, the numerical values of these factors being in theranges 0.8<Ku<1.07 and 0.8<Kl<1.07.